(1) Field of the Invention
The invention relates to helicopters and particularly to helicopters with an anti-torque device according to the preamble of claim 1.
(2) Description of Related Art
A configuration of a current rotary wing flying machine, e.g. a helicopter, comprises a main rotor, which in operation transmits a torque around a yaw axis of the helicopter. In operation this torque is countered by an empennage with typically an anti-torque device, such as a tail rotor, a shrouded tail rotor, i.e. a so called Fenestron, and a vertical fin. Exception made for the fin, all other anti-torque devices need power in order to provide this anti-torque needed for a helicopter operating properly.
Additionally a typical helicopter configuration needs a horizontal stabilizer for pitch stability by generating negative lift in order to keep the helicopter fuselage in a proper, horizontal position during a typical forward flight. In additional flight conditions, such as push-over, pull-out, etc., the horizontal stabilizer provides sufficient static and dynamic stability. The typical horizontal stabilizer has a fixed incidence angle, hence the force provided by the horizontal stabilizer cannot be changed by the pilot during flight. Therefore, the minimum drag fuselage attitude might not be fully achieved.
Gathering the information of the anti-torque designs of the state of the art, the following problems occur:
Fixed vertical and horizontal stabilizing surfaces only provide forces in said fixed directions;
Fixed vertical and horizontal stabilizing surfaces do not provide any additional propulsive force;
Open tail-rotors are a potential danger for humans and can be damaged by foreign objects;
The rotating devices cannot be easily changed in diameter without having major changes and re-designs of the entire helicopter.
Cross-Flow Fans with blades arranged to a torus-like configuration are known from the heating, ventilating and air conditioning field, providing an airflow passing the blades crosswise. Cross-Flow Fans are characterized by one dominant dimension, namely small in diameter and as long as needed.
The document GB 2316374 describes a cross-flow fan integrated in a lifting member, e.g. a wing, in order to create lift for an aircraft's airfoil.
The document GB 2346348 A describes a cross-flow fan integrated into a lifting member with additionally a movable lip in the ingestion area.
The document GB 2405624 A describes a cross-flow fan which is integrated into the rear section of an airfoil in order to control the flow around the airfoil. Additionally the document GB 2405624 A describes an enclosed housing which can be closed for cruise flight and opened for high-lift conditions as needed during take-off.
The document US 2012/0160955 A1 describes a hybrid rotor system for an aircraft which produces lift and thrust in order to propel an aircraft. This hybrid rotor system comprises a magnus rotor, a transverse flow rotor, i.e. a so called cross-flow fan, and a guide mechanism. In general US 2012/0160955 A1 relates only to aircrafts without an additional rotor system, so called cyclogyros, that pulls maximal airflow through both of propulsion and lifting surfaces. A cylindrical radial turbine is embedded in the wing with its axis parallel to the wing and leaving about ⅔ of the diameter exposed above the top side of the wing's length just after the leading edge. This increases the velocity of the airflow across the wing's upper surface beyond that of the forward motion of the aircraft. Consequently the wing of US 2012/0160955 A1 has lift at slow speeds where another wing would stall.
The document US 2013/0119186 A1 describes a helicopter with a fuselage and a tail boom, said helicopter being provided with a main rotor that rotates in operation about a rotation axis and, thus, produces a torque which acts on the fuselage. A cross-flow fan with a housing and a rotor is provided, said rotor being mounted in the housing, wherein the cross-flow fan is arranged on the tail boom of the helicopter such that it produces a thrust effect during operation which compensates for the torque produced by the main rotor. The housing comprises an air inlet and an air outlet, which is arranged at a position that is diametrically opposed to a position of the air inlet. The cross-flow fan produces an air flow that is perpendicular to its rotation axis.